His Dark Reflection (Heart and Haven 3) by Heloise West at Loose Id

Book Blurb

Disgraced FBI agent Nick Truman has failed to save his sister, held hostage by a drug cartel until he could give them Alex Crow, who eluded him. His epic downfall lands him in witness protection, where he plays by the rules and keeps to himself. But the murder of his neighbor brings danger to his door. He unexpectedly finds himself the champion of innocents and helplessly attracted to the homicide detective in charge of the case.

This can't end well.

Homicide Detective Hank Axelrod is good at digging out secrets, maybe because he hides a big one of his own. He also suspects his husband has one foot out of the door of their marriage and the specter of single life looms unpleasantly on the horizon.

A murder resembling another brings Nick into his world, a man who claims to be a mystery writer looking for a real life resource. Hank's instincts say he's more than that, and he's rarely wrong.

Torn between the errant soon-to-be-ex husband and the distracting, sexy stranger, Hank needs to focus all his attention on his murder case before he becomes the next victim.